The use of center pillar support structures in an automotive vehicle's side body structure is well known in the art. The typical center pillar support structure consists of one or more vertically positioned metal pieces extending from the vehicle's floor pan and rocker panel up to the vehicle's roof. The center pillar support structure is capable of supporting rear door hinge devices pivotally attached to a rear door, and usually accepts a striker that engages a latch on a vehicle's front door in order to releasably maintain the front door in a closed position. Generally, center pillar structures also define the areas of access to the passenger compartment through the front and rear doors, act as a columnar support structure between a vehicle's upper roof rail and lower side sill, and protect the vehicle's passengers against a side impact collision. Oftentimes, the center pillar structure provides additional protection against side impacts by integrating additional support members, such as reinforcing ribs (U.S. Pat. No. 6,607,239) or vertical reinforcement pillars (U.S. Pat. No. 5,246,264), inside the center pillar structure.
Many existing versions of a center pillar support structure are comprised of both an exterior side body panel made of mild steel, and an interior center pillar structure made of either high strength steel (HSS) or ultra high strength steel (UHSS). The use of HSS or UHSS, however, presents difficulties with the formability of the steel used to manufacture the interior center pillar structures to design specifications. The section of the interior center pillar support structure where an upper door hinge is attached, for example, is typically deep and narrow in geometry because it must meet a door hinge mounting surface on the exterior side body panel. This geometry makes it difficult to shape the HSS or UHSS to design specifications, and additionally creates problems with door hinge mounting accuracy that have previously been difficult to resolve.
The typical design for a center pillar support structure is also vulnerable to buckling or kinking during a side impact collision, causing damage to the vehicle's frame that is expensive and difficult to repair. Most center pillar structures, for example, become narrower as they move from their attachment point at the base of the lower side sill or floor pan to their attachment point at the upper roof rail; this narrowing is utilized in part to minimize obstruction of the view through the door windows. As a result, because the upper portion of the center pillar is smaller and narrower than at the pillar's base, it is not capable of absorbing as much energy as the lower portion of the pillar. During a side impact collision, energy is transferred from the rear door to the vehicle frame mainly through upper and lower door hinge patches mounted on the inside surface of the interior center pillar structure. Thus, if the upper door hinge patch has to absorb too much energy during a side impact, the upper portion of the center pillar structure tends to buckle or kink before the lower door hinge patch can assist in dispersing the side impact energy to the rest of the vehicle frame.